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A nuclear reactor is an enormous and extremely complex apparatus made up of 30,000 to 40,000 parts. Fuel rods which create thermal energy inside a nuclear power plant reach extremely high temperatures and contain a large quantity of radioactive material. Therefore, various safety measures are implemented at nuclear power plants to prevent such hazardous material from leaking outside. [Source: Yomiuri Shimbun, March 17, 2011]

The safety measures are based on three basic principles--stopping, cooling and confining. When pressure inside a nuclear reactor increases rapidly due to abnormal nuclear fission or for other reasons, stopping the reactor is the top priority. All control rods are inserted simultaneously to automatically stop the reactor. If that fails to bring operations to a halt, a large quantity of solution containing boric acid--which absorbs neutrons--is poured inside the reactor to stop nuclear fission.” [Ibid]

According to the Yomiuri Shimbun: “Sometimes the coolant water inside a nuclear reactor is lost for some reason. To prepare for such an eventuality, reactors are equipped with an emergency core cooling system (ECCS), which pours a large quantity of water inside the reactor to cool the fuel rods. Reactors are also equipped with a device that lowers the pressure inside the reactor in order to cool extremely hot steam that has leaked into the containment vessel.” [Ibid]

“The last layer of defense in terms of nuclear plant safety measures is the structure in which radioactive material is encased, comprising five protective layers. Firstly, pieces of uranium fuel are fired into pellets, as with ceramics, so that radioactive material produced as a result of nuclear fission is confined in the fuel rods. Secondly, the pieces of fuel are encased in tubes made of a zirconium alloy, capable of enduring extreme heat. As long as the tubes are not damaged, the radioactive material in the fuel rods will not leak outside.”

“The third is a pressure vessel made of thick steel. Even if the tubes are ruptured, the cylindrical vessel can keep radioactive material contained inside the valves. The fourth is a steel containment vessel that houses the pressure vessel, pipes, control rods, recirculation pumps and other key components. Around the containment vessel there are pools to store used fuel rods and various control devices. These are housed within the outer containment building. The building's walls comprise the fifth layer of protection. They are made of one- to two-meter-thick concrete, which prevents radioactive rays from leaking to the external environment. For extra safety, the building has no windows.”

Links to Articles in this Website About the 2011 Tsunami and Earthquake: 2011 EAST JAPAN EARTHQUAKE AND TSUNAMI: DEATH TOLL, GEOLOGY AND THEORIES Factsanddetails.com/Japan ; ACCOUNTS OF THE 2011 EARTHQUAKE Factsanddetails.com/Japan ; DAMAGE FROM 2011 EARTHQUAKE AND TSUNAMI Factsanddetails.com/Japan ; EYEWITNESS ACCOUNTS AND SURVIVOR STORIES Factsanddetails.com/Japan ; TSUNAMI WIPES OUT MINAMISANRIKU Factsanddetails.com/Japan ; SURVIVORS OF THE 2011 TSUNAMI Factsanddetails.com/Japan ; DEAD AND MISSING FROM THE 2011 TSUNAMI Factsanddetails.com/Japan ; RESCUE, RELIEF, REBUILDING AFTER TSUNAMI Factsanddetails.com/Japan ; LIFE FOR SURVIVORS AFTER THE TSUNAMI Factsanddetails.com/Japan ; CRISIS AT THE FUKUSHIMA NUCLEAR POWER PLANT Factsanddetails.com/Japan ; TEPCO, AND THE SAFETY OF FUKUSHIMA NUCLEAR PLANT Factsanddetails.com/Japan ; MELTDOWNS AT THE FUKUSHIMA Factsanddetails.com/Japan ; EARLY HOURS AT FUKUSHIMA AFTER THE TSUNAMI STRUCK Factsanddetails.com/Japan ; WHO’s TO BLAME FOR THE FUKUSHIMA Factsanddetails.com/Japan ; DAMAGE CONTROL AT FUKUSHIMA NUCLEAR POWER PLANT Factsanddetails.com/Japan ; RADIATION RELEASED FROM FUKUSHIMA Factsanddetails.com/Japan ; IMPACT OF EARTHQUAKE AND TSUNAMI OF MARCH 11, 2011 ON TOKYO, TRANSPORTATION AND ELECTRICITY Factsanddetails.com/Japan ; IMPACT OF 2011 EAST JAPAN EARTHQUAKE AND TSUNAMI ON THE ECONOMY Factsanddetails.com/Japan ; NUCLEAR ENERGY IN JAPAN Factsanddetails.com/Japan ;

Media Coverage of the Nuclear Crisis at Fukushima

A Wall Street Journal editorial printed three days after the March 11 earthquake and tsunami read: “After a once-in-300-years earthquake, the Japanese have been keeping cool amid the chaos, organizing an enormous relief and rescue operation, and generally earning the world's admiration. We wish we could say the same for the reaction in the U.S., where the troubles at Japan's nuclear reactors have produced an overreaction about the risks of modern life and technology.”

“Part of the problem is the lack of media proportion about the disaster itself. The quake and tsunami have killed hundreds, and probably thousands, with tens of billions of dollars in damage. The energy released by the quake off Sendai is equivalent to about 336 megatons of TNT, or 100 more megatons than last year's quake in Chile and thousands of times the yield of the nuclear explosion at Hiroshima. The scale of the tragedy is epic. Yet the bulk of U.S. media coverage has focused on a nuclear accident whose damage has so far been limited and contained to the plant sites. In simple human terms, the natural destruction of Earth and sea have far surpassed any errors committed by man.”

“Given the incomplete news reports, it is impossible to say how much worse the nuclear damage will be. Unlike the Soviets at Chernobyl, the Japanese have been taking sensible precautions like evacuating people near the plants and handing out iodine pills even if they may never be needed. These precautions increase public worry, but better to take them even if they prove to be unnecessary.”

Fukushima Crisis Rated as Bad as Chernobyl

In mid April 2011, the Nuclear and Industrial Safety Agency (NISA) raised the severity level of the crisis at the Fukushima No. 1 nuclear power plant to a seven with seven being the worst rating on its scale, equivalent to that of the 1986 Chernobyl crisis. The agency had previously rated the accident as a five. The agency---a Japanese government organization’said the amount of radioactive material, calculated based on the reactors' estimated condition, reached "more than several tens of thousands of terabecquerels." A terabecquerel equals 1 trillion becquerels. [Source: Yomiuri Shimbun, April 13, 2011]

The level is defined as a "major accident" under the International Nuclear and Radiological Event Scale (INES), or the highest level on its scale from zero to seven, based radiation releases and the effect or radiation on workers at the nuclear facility and people living around it. According to the agency, the total amount of iodine-131 and cesium-137 emitted between March 11 and April 12 reached 370,000 terabecquerels according to the reactors' estimated condition. Within this assessment, cesium levels were converted to their equivalent in iodine-131 levels. Another Japanese government agency---the Cabinet Office's Nuclear Safety Commission---calculated the total amount of iodine and cesium emitted between March 11 and April 5 was 630,000 terabecquerels (again, with cesium levels converted to the iodine equivalent).

Some felt that giving the Fukushima crisis the same ranking as Chernobyl was not right. The total amount of radioactive materials emitted thus far by the Fukushima plant is equal to about 10 percent of that released in the Chernobyl accident and no one has been killed the Fukushima crisis. In the Chernobyl crisis, about 5.2 million terabecquerels of radioactive material was emitted into the air in the space of 10 days and about 30 workers and firefighters there die of radiation exposure. The NISA---the group in charge of making the ranking for the International Atomic Energy Agency (IAEA)---decided to raise the INES level not only because of the calculated radiative material released into the atmosphere but also because of the widespread ramifications of the accident.

"Fukushima and Chernobyl are very different," said Denis Flory, head of nuclear safety and security at the IAEA. "This is a totally different accident. The level of releases and the value for Chernobyl are significantly different. IAEA officials, including the agency's chief Yukiya Amano, have repeatedly pointed out that Chernobyl---the world's worst-ever nuclear accident---was caused by human error and a design fault, whereas the crisis at Fukushima was triggered by an earthquake and ensuing tsunami of unprecedented size. In addition, the reactors at Fukushima had been automatically shutdown when the earthquake hit, while at Chernobyl the reactor had been operating. [Source: AFP, April 14, 2011]

"The mechanics of the accident are very different," Flory said. The Chernobyl reactor did not have a reactor vessel, while Fukushima does and that reactor vessel is still contained even after a series of explosions. That meant that the power of the Chernobyl explosion sent huge amounts of radiation into the high atmosphere "spreading it all over the world". By contrast, the Fukushima reactors were all shut down during the earthquake and there was no explosion in the reactor vessel itself.

“Out of Control” Reactors and Comparison’s With Chernobyl

Speaking about the damaged reactors at the Fukushima Daiichi nuclear plant, Guenther Oettinger, the European Union’s energy commissioner, said: “There is talk of an apocalypse and I think the word is particularly well chosen...The site is effectively out of control...In the coming hours, further catastrophic events can be expected with danger for the life and limbs of the people on the island.” Eric Besson, France’s minister of industry and energy, made similar remarks on Wednesday , telling BFM television: “Let’s not beat about the bush: they have visibly lost the essential of control. That is our analysis, in any case, it’s not what they are saying.” Yukiya Amano, the former Japanese diplomat who heads the IAEA said that the situation at the plant is “very serious,” but “it is not the time to say things are out of control.”


The British government's Chief Scientific Officer Professor John Beddington said that even in “the worst case scenario,” the crisis in Japan would not rival the one that engulfed the area around Chernobyl in 1986. According to a transcript of his remarks at the British Embassy in Tokyo he said, “If the Japanese fail to keep the reactors cool and fail to keep the pressure in the containment vessels at an appropriate level, you can get this, you know, the dramatic word “meltdown.” But what does that actually mean? What a meltdown involves is the basic reactor core melts, and as it melts, nuclear material will fall through to the floor of the container. There it will react with concrete and other materials---that is likely.”

“Remember this is the reasonable worst case,” Beddington said, “we don’t think anything worse is going to happen. In this reasonable worst case you get an explosion. You get some radioactive material going up to about 500 meters up into the air. Now, that’s really serious, but it’s serious again for the local area. It’s not serious for elsewhere, even if you get a combination of that explosion it would only have nuclear material going in to the air up to about 500 meters. If you then couple that with the worst possible weather situation, i.e. prevailing weather taking radioactive material in the direction of Greater Tokyo and you had maybe rainfall which would bring the radioactive material down, do we have a problem? The answer is unequivocally no. Absolutely no issue.”

“The problems are within 30 km of the reactor. And to give you a flavor for that, when Chernobyl had a massive fire at the graphite core, material was going up not just 500 meters but to 30,000 feet; it was lasting not for the odd hour or so but lasted months, and that was putting nuclear radioactive material up into the upper atmosphere for a very long period of time. But even in the case of Chernobyl, the exclusion zone that they had was about 30 kilometers. And in that exclusion zone, outside that, there is no evidence whatsoever to indicate people had problems from the radiation.”

The problems with Chernobyl were people were continuing to drink the water, continuing to eat vegetables and so on and that was where the problems came from. That’s not going to be the case here. So what I would really reemphasize is that this is very problematic for the area and the immediate vicinity and one has to have concerns for the people working there. Beyond that 20 or 30 kilometers, it’s really not an issue for health.

1/100 as Bad as Chernobyl

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Rachel Nolan wrote in the New York Times: “We know that the nuclear situation in Japan is critical. But how bad is it? Japan’s nuclear safety agency on Friday raised the rating of the crisis at Fukushima from 4 to 5 on the 7-step international scale. On one hand, this is scary: another Level 5 nuclear crisis was at Three Mile Island in 1979. (Chernobyl was a 7.) On the other hand, as a scientist friend pointed out to me this morning, the new rating means that the situation in Fukushima is 1/100 as bad as the Chernobyl accident. [Source: Rachel Nolan, New York Times]

“An explanation: The 7-step international scale was created by the International Atomic Energy Agency (I.A.E.A.) to measure the intensity of nuclear disasters,” Nolan wrote. “It is a logarithmic scale; an increase of one level means it is 10 times as intense, as the agency explains on a fact sheet. The Richter scale is also a logarithmic scale. But because it is much easier to systematically measure the shaking caused by an earthquake than to gauge a nuclear crisis, the I.A.E.A.’s scale is necessarily more interpretive. For example, no one died during the Three Mile Island meltdown, so saying that it was even 1 percent as bad as Chernobyl seems like an overestimation. And given Japan’s history, the psychological effects of Fukushima will most likely be much greater than those of Three Mile Island, so rating them both the same may also be misleading. But despite its flaws, the I.A.E.A. scale is the only international measure we’ve got.”

“There is the horrifying possibility that the rating at Fukushima will rise. If the 1970s movie “The China Syndrome” is your best reference for what a nuclear meltdown---the worst-case scenario---might look like, it is worth checking out an informative M.I.T. blog. Students at the nuclear science and engineering department do a sober job of explaining the science behind what is unfolding in Japan.

Breakdown of Nuclear Power Plant Safety at Fukushima Nuclear Power Plant

When the earthquake occurred, reactors Nos. 1, 2 and 3 at the Fukushima No. 1 nuclear power plant were in operation. Immediately after the huge tremor, the control rods were automatically deployed and the reactors were stopped. Events up until this stage were following their predicted course. However, fuel rods continue to give off extreme heat for a long time, even after reactors have ceased operating. Such heat could cause the coolant water inside the reactor to boil, leading to the risk of the reactor boiling dry. [Source: Yomiuri Shimbun, March 17, 2011]

The ECCS system is designed to prevent this from occurring. The system circulates water inside the reactor using electric power from sources other than the nuclear power plant itself, and also features a doughnut-shaped structure called a suppression pool, to cool high-pressure steam into water. Spent fuel rods removed from reactors need to be kept permanently cooled with circulating water. [Ibid]

However, in the Fukushima No. 1 plant, power generators for operating the ECCS system broke down. Although the generators were designed to keep operating even after very strong tremors, the tsunami that struck the plant on Friday was of a scale beyond what had been anticipated, and might have thrown seawater on the generators, nuclear experts said. [Ibid]

The temperature began to rise rapidly inside the reactor, which had lost its cooling functions. As a result, the metal tubes containing the fuel rods, comprising the second layer of protection, began melting down. In addition, the melted alloy caused a chemical reaction with the water, leading to a discharge of hydrogen. The hydrogen likely reacted with oxygen in the air inside the building, and it was this that caused the explosions. As a result, the No. 1 reactor building lost a large part of its walls, which constituted the fifth protection layer. [Ibid]

In the damaged reactors, the temperature continued to rise and a huge quantity of coolant water evaporated, leading to the risk that the exposed parts of the fuel rods above the water may melt. Although Tokyo Electric Power Co. workers poured seawater into the reactors using pump vehicles, the operation did not go smoothly due to the fear of contamination from radioactive material. Meanwhile, water used to cool spent fuel rods in the No. 4 reactor could no longer be circulated due to the loss of power. It is feared that exposure of the fuel rods to the air sparked a fire that led to leakage of the radioactive material contained therein. [Ibid]

Failure of TEPCO to Take Anti-Tsunami Measures

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Damage at another reactor in 2007
The Fukushima nuclear power plant was built to withstand a magnitude 7.5 earthquake and a 5.7-meter-high tsunami. The March 11 earthquake measured 9.0 on the Richter scale and the tsunami was over 10 meters high.

The Japanese nuclear establishment largely disregarded the potentially destructive force of tsunamis. The word did not even appear in government guidelines until 2006, decades after plants began dotting the Japanese coastline. Just a month before the March 11 earthquake and tsunami government regulators approved a 10-year extension for the oldest of the six reactors at Fukushima despite warnings about its safety. Several weeks after the extension was granted, the company admitted that it had failed to inspect 33 pieces of equipment related to the cooling systems, including water pumps and diesel generators, at the power station’s six reactors. [Source: Norimitsu Onishi and James Glanz, New York Times, March 26, 2011]

Norimitsu Onishi and James Glanz wrote in the New York Times, “Japanese government and utility officials have repeatedly said that engineers could never have anticipated the magnitude 9.0 earthquake ...that caused the sea bottom to shudder and generated the huge tsunami. Even so, seismologists and tsunami experts say that according to readily available data, an earthquake with a magnitude as low as 7.5---almost garden variety around the Pacific Rim---could have created a tsunami large enough to top the bluff at Fukushima.” [Ibid]

“After an advisory group issued nonbinding recommendations in 2002, TEPCO... raised its maximum projected tsunami at Fukushima Daiichi to between 17.7 and 18.7 feet---considerably higher than the 13-foot-high bluff. Yet the company appeared to respond only by raising the level of an electric pump near the coast by 8 inches, presumably to protect it from high water.” “We can only work on precedent, and there was no precedent,” said Tsuneo Futami, a former Tokyo Electric nuclear engineer who was the director of Fukushima Daiichi in the late 1990s. “When I headed the plant, the thought of a tsunami never crossed my mind.” [Ibid]

“The intensity with which the earthquake shook the ground at Fukushima also exceeded the criteria used in the plant’s design...Japan is known for its technical expertise. For decades, though, Japanese officialdom and even parts of its engineering establishment clung to older scientific precepts for protecting nuclear plants, relying heavily on records of earthquakes and tsunamis, and failing to make use of advances in seismology and risk assessment since the 1970s.” [Ibid]

“For some experts, the underestimate of the tsunami threat at Fukushima is frustratingly reminiscent of the earthquake---this time with no tsunami---in July 2007 that struck Kashiwazaki, a Tokyo Electric nuclear plant on Japan’s western coast.. The ground at Kashiwazaki shook as much as two and a half times the maximum intensity envisioned in the plant’s design, prompting upgrades at the plant. “They had years to prepare at that point, after Kashiwazaki, and I am seeing the same thing at Fukushima,” said Peter Yanev, an expert in seismic risk assessment based in California, who has studied Fukushima for the United States Nuclear Regulatory Commission and the Energy Department.” [Ibid]

“There is no doubt that when Fukushima was designed in the 1960s , seismology and its intersection with the structural engineering of nuclear power plants was in its infancy, Hiroyuki Aoyama, an expert on the quake resistance at the University of Tokyo, told the New York Times. Engineers employed a lot of guesswork, adopting a standard that structures inside nuclear plants should have three times the quake resistance of general buildings. “There was no basis in deciding on three times,” said Mr. Aoyama, an emeritus professor of structural engineering at the University of Tokyo. “They were shooting from the hip...There was a vague target.” [Ibid]

Evolution of Anti-Tsunami Measures at Fukushima Nuclear Power Plant

Norimitsu Onishi and James Glanz wrote in the New York Times, “When Japanese engineers began designing their first nuclear power plants more than four decades ago, they turned to the past for clues on how to protect their investment in the energy of the future. Official archives, some centuries old, contained information on how tsunamis had flooded coastal villages, allowing engineers to surmise their height. So seawalls were erected higher than the highest tsunamis on record. At Fukushima Daiichi, Japan’s fourth oldest nuclear plant, officials at Tokyo Electric used a contemporary tsunami---a 10.5-foot-high wave caused by a 9.5-magnitude earthquake in Chile in 1960---as a reference point.”[Source: Norimitsu Onishi and James Glanz, New York Times, March 26, 2011]

“The 13-foot-high cliff on which the plant was built would serve as a natural seawall, according to Masaru Kobayashi, an expert on quake resistance at the Nuclear and Industrial Safety Agency, Japan’s nuclear regulator. Eighteen-foot-high offshore breakwaters were built as part of the company’s anti-tsunami strategy, said Jun Oshima, a spokesman for Tokyo Electric. But regulators said the breakwaters---mainly intended to shelter boats---offered some resistance against typhoons, but not tsunamis, Mr. Kobayashi said.” [Ibid]

“We left it to the experts,” Masatoshi Toyoda, a retired TEPCO vice president who oversaw the construction of the plant, told the New York Times. “They researched old documents for information on how many tombstones had toppled over and such.”

Evolution of Anti- Earthquake and Tsunami Measures in Japan

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damaged pipe at TEPCO plant
“Over the decades, preparedness against tsunamis never became a priority for Japan’s power companies or nuclear regulators,” Onishi and Glanz wrote. “They were perhaps lulled, experts said, by the fact that no tsunami had struck a nuclear plant until two weeks ago. Even though tsunami simulations offered new ways to assess the risks of tsunamis, plant operators made few changes at their aging facilities, and nuclear regulators did not press them. Engineers took a similar approach with earthquakes. When it came to designing the Fukushima plant, official records dating from 1600 showed that the strongest earthquakes off the coast of present-day Fukushima Prefecture had registered between magnitude 7.0 and 8.0, Mr. Kobayashi said.” [Source: Norimitsu Onishi and James Glanz, New York Times, March 26, 2011]

“Eventually, experts on government committees started pushing for tougher building codes, and by 1981, guidelines included references to earthquakes but not to tsunamis, according to the Nuclear and Industrial Safety Agency. That pressure grew exponentially after the devastating Kobe earthquake in 1995, said Kenji Sumita, who was deputy chairman of the government’s Nuclear Safety Commission of Japan in the late 1990s.” [Ibid]

“Mr. Sumita said power companies, which were focused on completing the construction of a dozen reactors, resisted adopting tougher standards, and did not send representatives to meetings on the subject at the Nuclear Safety Commission. “Others sent people immediately,” Mr. Sumita said, referring to academics and construction industry experts. “But the power companies engaged in foot-dragging and didn’t come.”

“Meanwhile, the sciences of seismology and risk assessment advanced around the world. Although the United States Nuclear Regulatory Commission has come under severe criticism for not taking the adoption of those new techniques far enough, the agency did use many of them in new, plant-by-plant reviews, said Greg S. Hardy, a structural engineer at Simpson Gumpertz & Heger who specializes in nuclear plant design and seismic risk.” [Ibid]

“For whatever reasons---whether cultural, historical or simply financial---Japanese engineers working on nuclear plants continued to predict what they believed were maximum earthquakes based on records. Those methods, however, did not take into account serious uncertainties like faults that had not been discovered or earthquakes that were gigantic but rare, said Mr. Hardy, who visited Kashiwazaki after the 2007 quake as part of a study sponsored by the Electric Power Research Institute. [Ibid]

“The Japanese fell behind,” Mr. Hardy told the New York Times. “Once they made the proclamation that this was the maximum earthquake, they had a hard time re-evaluating that as new data came in.” The Japanese approach, referred to in the field as “deterministic”---as opposed to “probabilistic,” or taking unknowns into account---somehow stuck, said Noboru Nakao, a consultant who was a nuclear engineer at Hitachi for 40 years and was president of Japan’s training center for operators of boiling-water reactors. “Japanese safety rules generally are deterministic because probabilistic methods are too difficult,” Mr. Nakao said, adding that “the U.S. has a lot more risk assessment methods.” [Ibid]

“The science of tsunamis also advanced, with far better measurements of their size, vastly expanded statistics as more occurred, and computer calculations that help predict what kinds of tsunamis are produced by earthquakes of various sizes,” Onishi and Glanz wrote. “Two independent draft research papers by leading tsunami experts---Eric Geist of the United States Geological Survey and Costas Synolakis, a professor of civil engineering at the University of Southern California---indicate that earthquakes of a magnitude down to about 7.5 can create tsunamis large enough to go over the 13-foot bluff protecting the Fukushima plant. Mr. Synolakis called Japan’s underestimation of the tsunami risk a “cascade of stupid errors that led to the disaster” and said that relevant data was virtually impossible to overlook by anyone in the field.” [Ibid]

“The first clear reference to tsunamis appeared in new standards for Japan’s nuclear plants issued in 2006. “The 2006 guidelines referred to tsunamis as an accompanying phenomenon of earthquakes, and urged the power companies to think about that,” said Mr. Aoyama, the structural engineering expert. The risk had received some attention in 2002, when a government advisory group, the Japan Society of Civil Engineers, published recommended tsunami guidelines for nuclear operators--- but no concrete action was take then. [Ibid]

“Perhaps the saddest observation by scientists outside Japan is that, even through the narrow lens of recorded tsunamis, the potential for easily overtopping the anti-tsunami safeguards at Fukushima should have been recognized. In 1993 a magnitude 7.8 quake produced tsunamis with heights greater than 30 feet off Japan’s western coast that would have indicated the Fukushima nuclear power plant.” [Ibid]

Other Nuclear Reactors Affected by the Tsunami

TEPCO’s other Fukushima Facility---Fukushima No.2 nuclear power plant---was hit by tsunami waves between 6.6 meters and 14 meters high. The main facilities did not suffer serious flood damage as they occupied ground higher than the Fukushima No.1 nuclear power plant. Seawater pumps at the No.2 plant were damaged but TEPCO managed to lower temperatures in the plants reactors to 100 degrees C, enabling a shut down and the repair or replacement of the pumps. [Source: Yomiuri Shimbun]

Japan Atomic Power Co.'s Tokai No. 2 plant in Tokaimura, Ibaraki Prefecture, was hit by a 5-meter tsunami on March 11 but the plant's cooling systems kept functioning. After the Kashiwazaki-Kariwa nuclear plant was hit by the Niigata Prefecture Chuetsu Offshore Earthquake in July 2007, Japan Atomic Power decided to build anti-tsunami walls at the Tokai No. 2 plant. The walls were built to withstand a tsunami 5.7-meters high, up from about four meters. The safety measures proved their worth on March 11, protecting two of the plant's three emergency power sources. Construction had not been completed by the time the tsunami struck, but a finished section on the south side of the Tokai plant protected a seawater-intake pump needed to cool an emergency diesel power generator, which prevented a complete loss of power at the plant. [Source: Yomiuri Shimbun, April 17, June 12 2011]

Relatively new reactors in the earthquake and tsunami zone--- the Onagawa plant and the Japan Atomic Power Co.'s Tokai No. 2 power plant in Ibaraki Prefecture---did not suffer serious problems in the disaster.

The Japan Atomic Power Company, which operates the Tokaimura nuclear plant, just 70 miles north of Tokyo, said that the cooling system for one of its reactors failed because of the tsunami. “We then manually stopped one of our cooling systems,” company representative Masao Nakano told AFP. “But the other cooling systems and other pumps are working well, and temperatures of the reactor have continued to fall smoothly.” The Tokaimura plant was the scene of a deadly nuclear accident in 1999

Writing on Twitter, Lawrence McGinty, a science journalist for ITV News in Britain, suggested that the news from Tokaimura is “not as disturbing as [it] sounds,” since the reactor was “closed down when quake hit and has been cooling down for two days. Won’t be that hot.”

Onagawa Nuclear Power Plant

The Onagawa nuclear power plant, 45 miles from Sendai, in th heart of the tsunami-devastated area, was also hit hard by the March 11 tsunami. According to a statement posted on the IAEA website: “Japanese authorities have also informed the IAEA that the first (i.e., lowest) state of emergency at the Onagawa nuclear power plant has been reported by Tohoku Electric Power Company. The authorities have informed the IAEA that the three reactor units at the Onagawa nuclear power plant are under control.

Reuters reported that Japanese officials said the cooling systems at the Onagawa reactors had not failed: Japan’s nuclear safety agency said there was no problem with the cooling process at the Onagawa power plant and that a rise in radiation levels there was due to radiation leakage at another plant in a neighboring prefecture. The agency said a report from Tohoku Electric shows that cooling systems at all three reactors at the Onagawa complex, which were automatically shut after a massive earthquake and tsunami on Friday, are functioning properly.

Just after the March 11 earthquake, the tsunami hit Onagawacho, Miyagi Prefecture. The 15-meter-high wave destroyed most of the town and nearby fishing villages. Tohoku Electric Power Co.'s Onagawa nuclear power station at the mouth of Onagawa Bay was also struck by a 13-meter-high tsunami. Though its oil tanks and some buildings were damaged, the nuclear reactors and other key facilities were unharmed because they are located on a 14-meter-high hill. [Source: Yomiuri Shimbun, June 15, 2011]

About 90 minutes after the tsunami struck, about 40 residents of the town came to the nuclear plant. Cold and wet, and with snow falling, they were seeking shelter. Toshiyuki Aizawa, a spokesman of the plant, said: "Under the Nuclear Reactor Regulation Law, the power plant is off-limits to nonemployees. But plant manager Takao Watanabe knew that saving people's lives was more important. "So we opened up our plant's gym as a shelter so residents could use our oil stoves to stay warm. We live with the residents of this community every day, so we allowed all of them to enter the plant," he said.

Aizawa said that, at one point, 360 people were taking shelter in the plant and that plant workers provided clothes, blankets and meals. On June 7, the last evacuees moved to another shelter in town. Yutaka Abe, a 36-year-old fisherman who took shelter in the plant until June 6, said: "My house was swept away by the tsunami. So it was nice to have a roof over my head and a warm place to stay. The plant's gym was very clean, and I wasn't at all scared of the nuclear power plant."

On April 7, 2011, the Onagawa nuclear power plant in Miyagi Prefecture experienced a jolt from an aftershock associated with the March 11 quake that stronger than the plant was designed for.

New Levee and Sea Wall Prevented Total Power Loss at Nuclear Plant in Ibaraki

A nuclear power plant in Ibaraki run by Japan Atomic Power Co. avoided a station blackout from the March 11 tsunami thanks to a sea wall and levee it had almost finished extending and was reconstructing voluntarily. Kyodo reported: A government panel investigating the nuclear crisis at the Fukushima Daiichi power plant is analyzing measures taken by the company at the Tokai Daini atomic power plant on the assumption that the absence of such steps would have led to a similar serious accident, a source close to the panel said. [Source: Kyodo, October 25, 2011]

Japan Atomic Power concluded in 2002 that in preparing measures to deal with tsunami at the Tokai plant in Tokai, Ibaraki Prefecture, waves as high as 4.86 meters should be anticipated, based on an evaluation technology adopted by the Japan Society of Civil Engineers, the company said. But the Ibaraki prefectural government requested that the company reevaluate the estimate after its own projection of flooding from tsunami, made public in October 2007, showed that tsunami waves in nearby areas could be as high as 6 to 7 meters, the company said.

Japan Atomic Power then changed its wave level assumption to 5.7 meters and started the reconstruction work in July 2009 to raise the height of the 4.9-meter levee at the plant to 6.1 meters to protect seawater pumps designed to cool an emergency diesel generator. The reconstruction work was almost completed by September last year, but the remaining work to fully cover cable holes on the levee was scheduled to take place before around May this year, the company said.

The tsunami that hit the Tokai plant in March was 5.3 to 5.4 meters in height, exceeding the company's earlier estimate but around 30 to 40 centimeters lower than the later assumption. Hit by the tsunami, the Tokai plant suffered a loss of external power as experienced by the Fukushima Daiichi complex. The levee was overrun, causing one of three seawater pumps to fail, but the power plant succeeded in achieving a stable reactor condition known as cold shutdown with an emergency diesel generator cooled by the two remaining seawater pumps.

How Other Nuclear Reactors Would Stand Up Against a Tsunami

A study by the Japan Society of Maintenology, an organization of industrial facility maintenance experts, determined that at least 37 of the 54 nuclear reactors in Japan would be able to withstand tsunami as powerful as the one that hit the Fukushima No. 1 nuclear power plant on March 11, claims to have proved through its research. [Source: Yomiuri Shimbun, July 18, 2011]

The research covered 37 reactors’specifically, all the reactors in the nation that are not operated by Tokyo Electric Power Co. Taking into account emergency safety measures implemented at nuclear power plants after the March 11 disaster, which included raising the respective plants' maximum expected tsunami height by 9.5 meters, the JSM concluded that should tsunami strike, a serious accident--such as damage to a reactor's core--would not occur.

The cooling functions of reactors would continue to operate safely, even if they were hit by tsunami as large as the one that struck the Fukushima No. 1 nuclear power plant on March 11, the JSM concluded. The research was based on a scenario in which external and emergency power sources were disabled due to an earthquake and subsequent tsunami.

In August 2011 the Nuclear and Industrial Safety Agency announced there are 14 potentially active fault lines in areas near the crisis-hit Fukushima No. 1 nuclear power plant and other nuclear-related facilities. The 14 faults discovered to be potentially active were previously considered unlikely to cause earthquakes. According to the research, a magnitude-7.6 earthquake could occur on the potentially active Hatakawa fault line in Fukushima Prefecture, the largest magnitude earthquake estimated.

Image Sources: TEPCO, Greenpeace

Text Sources: New York Times, Washington Post, Los Angeles Times, Times of London, Yomiuri Shimbun, Daily Yomiuri, Japan Times, Mainichi Shimbun, The Guardian, National Geographic, The New Yorker, Time, Newsweek, Reuters, AP, Lonely Planet Guides, Compton’s Encyclopedia and various books and other publications.

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© 2008 Jeffrey Hays

Last updated April 2012

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